292 



May 1907. 



PLANT SANITATION. 



Root Diseases of Tea. 



By T. Fetch. 

 (Illustrated.) 



The literature of the plant diseases of any country shows that our knowledge 

 of them always follows the same course of evolution. Leaf diseases always come 

 into prominence first; when the cultivator has grasped the idea that a plant can 

 suffer from defiuite diseases, he finds that stems are also liable to be attacked ; and, 

 in due time, he arrives at the conclusion that even roots are not immune. Ceylon 

 exhibits the development of these phases in a marked degree. Coffee leaf disease 

 was followed by tea leal' disease ; then came cacao canker, and after some years, tea 

 root disease. But it must not be assumed from this sequence, that there was no 

 "canker" in the days of coffee, or no root disease in the early days of "Grey 

 Blight." There is little doubt that such diseases existed though their effects may 

 have been masked by the more prevalent leaf diseases, Moreover, there is always a 

 tendency to attribute all diseases to one cause, and it generally happens that what is 

 at first thought to be one disease proves on further examination to be half a dozen. 

 As has been pointed out before, this sub-division does not indicate a greater amount 

 of disease, but it may in some cases, with a fuller knowledge of the fungi, suggest 

 other methods of dealing with them. 



The Peradeniya Circular on "Root Disease in Tea" (Vol. II., No. 6, July, 

 1903,) refers briefly to the possibility that the great variability observed in the 

 appearance of the roots of tea bushes killed by root disease may indicate that the 

 cause is not in all cases the fungus {Rosellinia radiciperda, Mass.) therein described. 

 It has now been ascertained by numerous cultivations of the mycelium on dead or 

 dying roots, that there are several distinct fungi which attack the roots of tea, and 

 judging from the number of specimens submitted, Rosellinia is one of the less 

 common of these. 



Upcountry Tea Root Disease. 



The root disease which appears to be most prevalent above 4,000 feet is easily 

 distinguished from Rosellinia. When the dying bush is uprooted in the ordinary 

 way, the root is seen to be covered with small white raised patches or knobs, seldom 

 exceeding one-tenth of an inch in diameter. The margin of these nodules is reddish, 

 and in some cases there may be also coarse reddish strands spreading over the 

 surface of the root. From these nodules a mycelium spreads to other roots ; this is 

 white at first, but subsequently forms a thick cord with a tough red coat. The 

 mycelium between the bark and the wood forms a thin continuous white sheet. In 

 the majority of cases, the root decays completely and can be rubbed into powder ; 

 frequently one finds, on breaking it up, a thin gelatinous red sheet extending across 

 the dead root, but I have not yet seen any fructification on tea bushes in the field. 



But by cultivation under suitable conditions, the fructification is easily 

 obtained. This generally appears on the stem just above ground ; it may, however, 

 grow out horizontally on the surface of the soil, and in one cultivation the mycelium 

 spread downwards from the root and produced the fructification on the under surface 

 of the flower pot. The latter occurrence illustrates the travelling power of the 

 fungus. The fructification (sporophore) forms a white or pinkish patch, several 

 inches in diameter, studded with minute holes, adhering to the stem. Beneath the 

 comparatively soft upper tissue, and lying next to the wood or soil, is a red horny 



